我正在尝试在我的应用中添加一个简单的绘图活动。该活动允许我绘制，但当我尝试更改颜色时出现错误。当我从Activity调用DrawingView方法时出现错误。调试器不允许我在方法内部。
logcat中显示以下错误：
java.lang.IllegalStateException: Could not execute method of the activity
at android.view.View$1.onClick(View.java:4020)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.view.View$1.onClick(View.java:4015)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.reitron.putmaster.ActDrawingView.setColoring(java.lang.String)' on a null object reference
我有一个活动，一个DrawingView类和一个布局。
以下是活动的相关代码：
onCreate中的：
drawView = (ActDrawingView)findViewById(R.id.drawing);
LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
currPaint = (ImageButton)paintLayout.getChildAt(0);
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
public void paintClicked(View view){
//use chosen color
if(view!=currPaint){
//update color
ImageButton imgView = (ImageButton)view;
String color = view.getTag().toString();
drawView.setColoring(color);
// drawView.setColor(color);
imgView.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint));
currPaint=(ImageButton)view;
}
}
DrawingView类的代码：
public class ActDrawingView extends View {
private Path drawPath; //drawing path
private Paint drawPaint, canvasPaint; //drawing and canvas paint
private int paintColor = 0xFF000000; //initial color
private Canvas drawCanvas; //canvas
private Bitmap canvasBitmap; //canvas bitmap
public ActDrawingView(Context context, AttributeSet attrs) {
super(context);
setUpDrawing();
}
private void setUpDrawing() {
// get drawing area for interaction
drawPath = new Path();
drawPaint = new Paint();
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(20);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
//view given size
super.onSizeChanged(w, h, oldw, oldh);
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
//draw view
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
//detect user touch
float touchX = event.getX();
float touchY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
invalidate();
return true;
}
public void setColoring(String newColor){
//set color
invalidate();
paintColor = Color.parseColor(newColor);
drawPaint.setColor(paintColor);
}
}
以下是布局文件中的摘要
<com.reitron.putmaster.ActDrawingView
android:id="@+id/drawing"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_marginBottom="3dp"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_marginTop="3dp"
android:layout_weight="1"
android:background="#FFFFFFFF" />
<ImageButton
android:layout_width="@dimen/large_brush"
android:layout_height="@dimen/large_brush"
android:layout_margin="2dp"
android:background="#FFFF0000"
android:contentDescription="@string/paint"
android:onClick="paintClicked"
android:src="@drawable/paint"
android:tag="#FFFF0000" />
请你能帮我找到错误吗？
的Tx！
答案 0 :(得分：1)
您正尝试在可能缺失或尚未初始化的对象上调用.setColoring(color)。在你的情况下，我可以看到drawView是有问题的。你在这里调用它：
drawView = (ActDrawingView)findViewById(R.id.drawing);
，但我认为如果你在我刚刚提到的调用点（{1}}处放置一个断点，将返回null（也就是说它还没有找到视图。确保这个图形已正确初始化（也许放在它上面）在布局文件夹中（我认为它应该是它的视图（我可能是错的））））并再试一次。然而，错误点就在那里..